Meredith....
Unfortunately there are very few books that have much information about bichirs.
Probably the best available (though out of print, it can be found on Amazon.com) is Jurassic Fishes by Kotera, et al. It is a T.F.H. book and has information on bichirs, bony-tongues (arowanas, arapaima, etc.), Mormyrids, Gars, FW Stingrays, etc. There are some inaccuracies in identification of the bichir pictures but the general text is pretty good.
For a good picture book showing all of the species (and subspecies) of Polypterus and Erpetoichthys there is the Aqualog Polypterus book by Frank Schafer. While I don't agree with some of his taxonomy, he does have excellent pictures of all of the types of bichir and a little bit of information on recognition and husbandry. This book is quite expensive!
The new T.F.H. Encyclopedia of Exotic Tropical Fishes (Axelrod and Scott) has a small (by no means exhaustive) section on bichirs but somehow the text to accompany the picture of Polypterus palmas polli got mixed up with that for a swordtail or platy. Other than that minor annoyance, the book is a nice resource to have for all aspects of fish-keeping.
-Joe